Synergistic effects of niobium oxide (Nb2O5) on the Ru/Al2O3, where the alumina had boehmite phases prepared by sol-gel method with subsequent co-impregnation of bimetallic Ru-Nb, were investigated for an aqueous-phase hydrodeoxygenation (APH) as well as aqueous-phase reforming (APR) reaction of glycerol to form gaseous hydrocarbons and hydrogen with useful liquid-phase glycols such as ethylene and propylene glycols. The promoting effects of the Nb2O5 on the prototype Ru/Al2O3 were mainly attributed to the stabilized boehmite structures with the help of an incorporation of niobium oxides, which largely increased the catalytic activity and stability through less aggregations of smaller Ru nanoparticles. At an optimal Nb/Ru molar ratio of similar to 1, the much smaller Ru nanoparticles were highly dispersed on the Nb-incorporated alumina matrices on the hexa-coordinated Al3+ sites selectively even after hydrothermal aqueous-phase reactions. The highly dispersed Ru nanoparticles on the Lewis acid sites of the boehmite phase of Al2O3 surfaces showed a facile reducibility and larger metallic Ru surface area with less formations of inactive hard coke precursors. It was mainly originated from the preferential presence of the reduced metallic Ru nanoparticles on the surfaces of the acidic Nb2O5-modified boehmite, which can strongly anchor the active Ru metals with their smaller sizes.